It is known that a battery has internal resistance, and that the lower its temperature, the higher its internal resistance. Such an increase in internal resistance reduces the performance of the battery to the point that said battery can no longer deliver sufficient power to the equipment to which it is connected.
In order to remedy that drawback, it has been imagined to associate the battery with an external heater device, e.g. including reagents which, when associated with one another, generate an exothermal reaction in the vicinity of the battery. Unfortunately, such a device would be relatively heavy and would require firstly a quantity of reagents that is sufficient for heating up the battery to be available, and secondly those reagents to be replaced once they are used up. That results in logistics constraints that are prohibitive for certain applications, in particular in places to which access is difficult.
It has also been imagined to surround the case of the battery with a resistor and to cause the battery to discharge into the resistor in order to heat the battery. The battery-and-resistance assembly would then have to be insulated thermally in order to obtain effective heating. Unfortunately, that would increase the volume and the weight of the battery and would be relatively costly while also offering relatively low efficiency, and the core temperature of the cells would rise slowly.